37 



and in moist rather than in dry climates 1 . But on all these 

 points reliable statistics are wanting. As regards seasons, 

 one author has declared that threadworms are commoner in 

 Autumn, another says in Spring 2 . The statistics of GBIBBOHM 

 and others do not give any conclusive indications of a seasonal 

 influence. 



Food. 



It has already been stated that the ova of Oxyuris are more 

 often swallowed with vegetable than with animal food, especi- 

 ally if the former be eaten uncooked. The eggs, which are 

 floating in the air, settle on vegetables, or they may be con- 

 veyed in manure or by sewage water, to the growing vegetables. 

 Thus salads, lettuces, watercress and the like, which are not 

 usually cooked, are specially dangerous, but it appears certain 

 that carrots, cabbages, onions, etc., may convey the infection, 

 even though they are cooked. One author of repute considers 

 strawberries the greatest offenders amongst fruits. 



Bodily Condition or Constitution. 



Most authorities believe this to be the most important 

 factor amongst predisposing conditions. Nearly all experience 

 seems to show that weakly persons are more subject to in- 

 fection than the strong 3 , and this appears to be borne out by 

 the age -distribution of the complaint : children and old 

 people the greatest sufferers show, naturally, more sus- 

 ceptibility to morbid influences than adults. This liability 

 to '' worms " has been explained as due to a peculiar condition 

 of the gastric juice, which, in those habitually afflicted with 

 intestinal parasites, apparently lacks the power of destroying 

 the embryos of Oxyuris as they reach the stomach, within 

 their ova. 



1 " Vermes . . . rusticos prae wenigstens hat man um diese Zeit 

 urbanis . . . aera humidum hauri- die meisten an Oxyuris leidenden 

 entes . . . prae contrariis in- Kranken constatirt." (BRASS, A., 

 festare creditur ; et magna ex parte Die thierischen Parasiten des Men- 

 cerium est." (WALLIS, T., Disser- schen, Cassel, 1884, p. 62.) 

 tatio medico, inauguralis de vermibus 3 " L'oxyure vermiculaire se 

 intestinorum, Edinburgi, 1784, p. 26.) trouve . . . surtout chez les 

 " Besonders zu Ende des Win- enfants ou les hommes soumis a 

 ters scheint die Entwickelung am un regime debilitant." (DUJARDIN, 

 energischsten vor sich zu gehen, M. F., op. cit., p. 139.) 



